Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 290850 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 350 AM EST MON DEC 29 2014 .SYNOPSIS...
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STRONG HIGH PRESSURE BUILDS SOUTH FROM WESTERN CANADA AND THEN SPREADS ACROSS THE USA FOR MUCH OF THE WEEK. THIS WILL MEAN A DRY AND COLD SPELL FOR NEW ENGLAND THROUGH THE END OF THE WEEK. A STORM MAY IMPACT THE REGION SOMETIME LATER IN THE WEEKEND BUT THERE IS MUCH UNCERTAINTY REGARDING POSSIBLE OUTCOMES.
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&& .NEAR TERM /THROUGH TODAY/...
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NEAR ZONAL FLOW ACROSS GT LAKES AND NEW ENG WITH THE MAIN FEATURE BEING A STRONG AND SPRAWLING HIGH PRES /1060 MB/ ACROSS WESTERN CANADA. RIDGING FROM THIS HIGH PRES EXTENDS EAST ALL THE WAY THROUGH THE GT LAKES AND INTO NEW ENG WITH DRY NW FLOW PROVIDING PT-MOSTLY SUNNY SKIES AND COLDER TEMPS. THE COLUMN IS MAINLY DRY BUT SOUNDINGS DO SHOW SOME LOW LEVEL MOISTURE TO SUPPORT SCT-BKN CU ESPECIALLY IN THE INTERIOR...WHILE HIGH CLOUDS MAY LINGER THIS MORNING ALONG THE S COAST. SOUNDINGS SHOW MIXING UP CLOSE TO 850 MB TODAY WHERE TEMPS ARE -8 TO -11C. THIS SUPPORTS MAX TEMPS RANGING FROM MID 30S HIGHER TERRAIN IN NORTHERN/WESTERN MA TO LOWER 40S COASTAL PLAIN. MAY SEE SOME NW GUSTS TO 20 MPH IN THE MORNING THEN DIMINISHING THROUGH THE AFTERNOON.
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&& .SHORT TERM /TONIGHT THROUGH 6 PM TUESDAY/...
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THE LARGE HIGH PRES FROM WESTERN CANADA BUILDS SOUTH INTO THE PLAINS DURING TUE WITH RIDGING EXTENDING TO THE EAST COAST. CONTINUED DRY NW FLOW WILL BRING MOCLEAR SKIES TONIGHT AND TUE AS LOW LEVEL MOISTURE DECREASES...BUT TURNING EVEN COLDER AS 850 MB TEMPS DROP TO -13 TO -16C TUE. LOWS TONIGHT WILL BE IN THE TEENS TO LOWER 20S...WITH HIGH TEMPS TUE RECOVERING TO LOW/MID 30S...EXCEPT UPPER 20S HIGHER TERRAIN. MODEST NW BREEZES EXPECTED TUE.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
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HIGHLIGHTS... * DRY THROUGH AT LEAST FRIDAY NIGHT * SEASONABLE TO A LITTLE BELOW NORMAL TEMPERATURES * CHANCE OF RAIN OR SNOW DEVELOPING SOMETIME OVER THE WEEKEND OVERVIEW... MEDIUM RANGE MODELS REMAIN IN GOOD AGREEMENT THROUGH THE WORK WEEK BUT ARE DEPICTING WIDELY VARYING SOLUTIONS FOR NEXT WEEKEND IN HANDLING THE TROF BEING EJECTED OUT OF THE SOUTHWEST USA. THE TIMING OF THE EJECTION OF THAT TROF WILL BE CRITICAL. A FASTER TIMING WOULD SEEM TO RESULT IN BETTER PHASING WITH THE NORTHERN STREAM AND A POTENT SYSTEM HEADING TOWARD THE GREAT LAKES. THE 00Z GFS AND UKMET OPERATIONAL RUNS AS WELL AS ENSEMBLE MEMBERS FROM PRIOR RUNS DEPICT THIS TYPE OF SCENARIO. THE RESULT FOR SOUTHERN NEW ENGLAND WOULD BE A PERIOD OF VERY MILD...WET AND WINDY SENSIBLE WEATHER. A SLOWER EJECTION OF THE TROF WOULD APPEAR TO ALLOW THE NORTHERN STREAM TO ESTABLISH GREATER DOMINANCE AND CAUSE THE SW TROF TO SHEAR TOWARD THE EAST COAST WITH A SURFACE LOW PASSING SE OF NEW ENGLAND WITH COLD AND POSSIBLY SNOWY SENSIBLE WEATHER LATE IN THE WEEKEND OR EARLY THE FOLLOWING WEEK. WITH SIGNALS OF A RETURN TO A POSITIVE NAO BY THE END OF THE WEEK...IT SEEMS THAT THE EVENTUAL SOLUTION SHOULD BE FAIRLY PROGRESSIVE WITH A DEEP COASTAL LOW UNLIKELY. BOTTOMLINE...CONFIDENCE IN NEARLY ALL ELEMENTS OF THE FORECAST FOR THIS WEEKEND IS VERY LOW. THERE IS AN EXCEPTIONALLY WIDE RANGE OF POSSIBILITIES FOR TEMPERATURE...WIND DIRECTION/SPEED...PTYPE... QPF...AND TIMING OF ANY PRECIPITATION. DAY TO DAY... TUE NIGHT THROUGH WED...GENERALLY DRY AND COLDER THAN NORMAL TEMPERATURES SUPPORTED BY BROAD TROF ALOFT CENTERED OVER HUDSON BAY AND STRONG HIGH SPREADING S AND SE FROM THE CANADIAN AND USA HIGH PLAINS. TUE NIGHT/WED AM LOOKS TO BE THE COLDEST NIGHT WITH 850 MB TEMPERATURES OF -15C TO -17C...PROBABLY MOSTLY CLEAR SKIES AND LIGHT WINDS. WILL LIKELY EXPERIENCE SURFACE TEMPERATURES IN TEENS ACROSS MOST OF INTERIOR SOUTHERN NEW ENGLAND WITH POSSIBLY POCKETS OF 5 TO 10 ABOVE TEMPERATURES NW MA. LACK OF SNOWCOVER PREVENTS WHAT MIGHT OTHERWISE BE COLDER TEMPERATURES. HIGH TEMPERATURES ON WED WILL LIKELY TOP OUT IN THE MID 20S TO LOWER 30S MOST LOCATIONS. WED NIGHT AND THU...THERE ARE A COUPLE OF ISSUES DURING THIS TIME PERIOD. ONE IS THAT BELIEVE THERE IS A CHANCE OF SOME LIGHT OCEAN EFFECT SNOW SHOWERS OVER NANTUCKET LATE WED NIGHT AND THU MORNING. GIVEN SEA SURFACE TEMPERATURES STILL MID TO UPPER 40S OFF THE NEW ENGLAND SOUTH COAST...ANTICIPATE STEEP ENOUGH LAPSE RATES TO SUPPORT SCATTERED FLURRIES OR SNOW SHOWERS IN WSW FLOW THAT DEVELOPS ACROSS SOUTH COASTAL AREAS LATE WED NIGHT AND THU. BUFKIT SOUNDINGS SUPPORT LOW CHANCE POPS AT NANTUCKET...MAINLY IN THE 2 TO 10 AM TIME FRAME. SECOND ISSUE IS THE TIGHTENING SURFACE PRESSURE GRADIENT THAT SHOULD RESULT IN BRISK WINDS WITH GUSTS 20 TO 25 MPH OVER LAND AND POSSIBLY MARGINALLY GALE FORCE OVER THE OUTER COASTAL WATERS SOUTH AND SOUTHEAST OF NEW ENGLAND. THU NIGHT THROUGH FRI NIGHT...ANTICIPATE DRY CONDITIONS THROUGH THIS PERIOD WITH TEMPERATURES NEAR OR A LITTLE BELOW NORMAL. SAT THROUGH SUN...THIS IS WHEN THE FORECAST GETS VERY CHALLENGING. HAVE GONE WITH A MODEL CONSENSUS DUE TO THE EXTREME UNCERTAINTY. AS NOTED ABOVE...THERE EXISTS A WIDE RANGE OF POSSIBLE OUTCOMES DEPENDING UPON THE TIMING OF THE EJECTION OF THE TROF ENERGY FROM THE SOUTHWEST USA. FOR NOW...HAVE LOW CHANCE POPS FOR MUCH OF THE WEEKEND DUE TO UNCERTAINTY IN TIMING BUT DO NOT REALLY ANTICIPATE A PROLONGED EVENT. HAVE LOWERED HIGH TEMPERATURES SOME FROM PRIOR FORECASTS BUT HERE AGAIN THERE EXISTS AN EXTRAORDINARY WIDE RANGE OF POSSIBILITIES DEPENDING UPON WHETHER WE EXPERIENCE A ROBUST SYSTEM PASSING WELL WEST OF THE REGION OR A WEAK SYSTEM PASSING SOUTHEAST OF OUR AREA.
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&& .AVIATION /07Z MONDAY THROUGH FRIDAY/...
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FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. THROUGH 12Z...VFR. GRADUAL CLEARING. TODAY THROUGH TUESDAY...HIGH CONFIDENCE. VFR. NORTHWEST WINDS GUSTING 15-20 KTS TODAY. KBOS TERMINAL...HIGH CONFIDENCE. KBDL TERMINAL...HIGH CONFIDENCE. OUTLOOK...TUESDAY NIGHT THROUGH FRIDAY... HIGH CONFIDENCE OF MAINLY VFR THROUGH THE PERIOD. THE ONLY EXCEPTION IS A RISK OF MVFR CIGS AND VSBYS IN POSSIBLE OCEAN EFFECT SNOW SHOWERS INVOF NANTUCKET LATE WED NIGHT INTO THU MORNING.
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&& .MARINE...
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FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH TUESDAY/...HIGH CONFIDENCE. NW WINDS LIKELY TO REMAIN BELOW SCA THRESHOLDS THROUGH TUE WITH GUSTS TO 20 KT...BUT A FEW HIGHER GUSTS POSSIBLE THIS MORNING. SCA IN EFFECT UNTIL 8 AM FOR OUTER WATERS FOR SEAS UP TO 5 FT...OTHERWISE SEAS BELOW SCA THRESHOLDS. OUTLOOK...TUESDAY NIGHT THROUGH FRIDAY... TUE NIGHT THROUGH WED NIGHT...EXPECT WINDS AND SEAS BELOW SMALL CRAFT ADVISORY THRESHOLDS. THU...W WIND WILL LIKELY INCREASE ABOVE SMALL CRAFT ADVISORY THRESHOLDS ALL WATERS WITH A CHANCE OF GALE FORCE GUSTS OVER THE OUTER COASTAL WATERS.
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&& .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 8 AM EST THIS MORNING FOR ANZ254>256. && $$ SYNOPSIS...KJC/THOMPSON NEAR TERM...KJC SHORT TERM...KJC LONG TERM...THOMPSON AVIATION...KJC/THOMPSON MARINE...KJC/THOMPSON

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